Cicada diet

The cicada sound disappeared after one and a half week interval, it always the way that sudden silence happens every year following Obon period. Probably the ceremony of fertilization and egg laying has over for the short period of time. I had an opportunity to observe Cicada Egg Laying this year and to take photos relatively easily as mentioned before.
As for egg laying, the laying tube had some enough strength in Physical property to peel and to dig into a piece of wood branch.
Further more, payed I some on observing food supplying system of them more carefully this time.
Cicada has not any mouth to crash food but a sharp needle, it means that their energy supply depends on sap only. Of course, Kiss needle has adequate Physical property to perform bringing in wood liquid.
The construction of the needle is not a simple pipe but a complicated design.
I wonder how it knows the position of duet of the branch?
Does it has any pumping power to inhale wood liquid or inhalation is  done only by capillary action of wood conduit?
As a proof, a sap leakage mark is observed after a cicada suction position.
Any chemical material wood be spouted on the tip of the needle?